One example of means for carrying out an assembling operation by rotating the rotary shaft of the work body to adjust the phase of the rotary shaft is a transmission-assembling station provided in a power unit-assembling line for an automobile. When an engine assembly and a transmission assembly assembled in the assembling line are to be integrally coupled to each other, an end of a main shaft of the transmission assembly is spline-coupled into a shaft hole in a crankshaft of the engine assembly. In this case, if the phase of a male spline of the end of the main shaft and the phase of a female spline of the shaft bore in the crankshaft are not matched with each other, the assembling of the transmission assembly and the engine assembly cannot be achieved. Therefore, it is necessary to match both of the phases with each other.
To carry out this operation, in a conventional engine and a transmission assembling apparatus described in Japanese Utility Model Publication No.3-37865, a socket is mounted at an end of an output shaft connected to a drive source for rotation, and in a state in which the socket is in engagement in a socket hole provided in an end of a crankshaft, the drive source is operated to continuously rotate the crankshaft in one direction, and a fitting auxiliary device is mounted on the transmission to match the phases of the socket and the socket hole.
In the above conventional assembling apparatus, however, the position of an axis of the output shaft provided with the socket is fixed and hence, if there is an error such as a looseness produced in position of the engine supported in a pallet, the socket mounted at the end of the output shaft cannot be smoothly brought into engagement in the socket hole provided in the end of the crankshaft. For this reason, it is necessary to match the phase of a male spline of the end of the main shaft with the phase of a female spline of the shaft bore in the crankshaft, and an operation for such matching is extremely troublesome. Moreover, in the conventional device, the crankshaft is continuously rotated in one direction and hence, an exclusive auxiliary device is required and for example, it is necessary to mount a swinging device on the transmission.